The present invention relates to a process and to an apparatus for increasing the fatigue strength or durability of components having different shapes and sizes, particularly large crankshafts by cold forming, such as hammering, in the highest stressed areas at section changes, such as at fillets and bore openings.
Increasing the fatigue strength of components in the highest stressed areas at section changes by cold forming, such as hammering is a known process, which is applied in different ways. However, usually forces are introduced into the components by means of commercially available striking tools, such as pneumatic hammers and hydraulic vibrators. The pneumatic hammer is mainly used manually, in such a way that with an estimated distance blows are given and these strike the component in unequal spacings and impact directions. It is clear that this process cannot lead to the maximum theoretically and empirically achievable fatigue strength as a result of the imprecision in the level of the force action, as well as in the spacing of such actions and consequently a necessary surface quality for avoiding reworking. The use of hydraulic vibrators, whose application is described in the journals Vestnik Masinostroenija 49/1969, pp 58-59 and Traktory i sel schozmasiny 10/1969, pp 41-42, requires a continuous turning of the same when working round components, so that it is not possible to obtain a heightwise and adequately accurately determinable impact spacing for avoiding reworking and achieving the maximum fatigue strength in the hammered area.